Excess weight gain during pregnancy leads to significant long-term metabolic morbidities in mothers and their offspring. More than 50% of reproductive age women in the US exceed weight gain guidelines during pregnancy as recommended by the Institute of Medicine. Lifestyle modification programs targeting healthy eating and regular physical activity are successful in controlling weight gain as well as preventing obesity related comorbidities in other at risk populations. However few lifestyle intervention studies have been conducted in pregnant women to manage gestational weight gain and none were successful in helping women adhere to the guidelines. Although pregnant women are believed to be a highly motivated population for accepting behavior change, they face several barriers to traditional in-person clinic weight management programs. We have successfully implemented lifestyle interventions for weight management through Telehealth technologies (Smartphone) to oven/veight and obese individuals and these are readily adaptable to pregnant women. Application of telehealth technologies to pregnant women may therefore successfully address these barriers and facilitate appropriate weight gain during pregnancy. The objective of this study "Expecting Success: Personalized weight management during pregnancy" is to implement a personalized gestational weight management program to oven/veight and obese pregnant women that focuses on healthy eating and achieving National physical activity recommendations. 300 primiparous overweight and obese women will be randomly assigned to receive either usual care or a personalized lifestyle program for weight management delivered in-person or remotely via a Smartphone. The lifestyle program involves weekly contact with counselors from week 13 of gestation until delivery. Clinical assessments will be obtained throughout pregnancy and in the mother and offspring during the first year postpartum. This study is significant because it seeks to prevent excess weight gain during pregnancy, a major health problem for pregnant women and their offspring. If successful, our Smartphone approach will provide a novel, efficacious and scalable intervention for weight management in pregnant women.